Dynamic Sealing Arrangement For Movable Shaft

ABSTRACT

A dynamic sealing arrangement for preventing leakage of a fluid along a shaft includes multiple seals and pressurized barrier sealant is presented. According to one aspect, at least three seals are arranged along the shaft with pressurized barrier sealant between the first and second seals and a collection area is provided between the second and third seals to collect any leakage that might occur. Collected leakage, if any, is ported to an output port. According to another aspect, a unitary seal block member is provided that supports the dynamic sealing arrangement for the shaft and defines a piston chamber and a drilled passageway connecting the piston chamber and barrier sealant pressurization chamber between two seals. A substantial amount of plumbing is self contained in a single body minimizing the need for additional components or complexity.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a continuation of co-pending U.S. patentapplication Ser. No. 10/440,507, filed May 15, 2003.

BACKGROUND

The dynamic sealing arrangement described herein pertains to sealassemblies and more particularly to pressurized dynamic sealarrangements.

The proposed use of a pressurized barrier sealant fluid between twoseals for fluid control apparatus such as pumps, valves and the like isgenerally known. For example, pressurized dynamic shaft sealingarrangements are disclosed in U.S. Pat. No. 5,746,435 to Arbuckle, U.S.Pat. No. 6,161,835 to Arbuckle, U.S. Pat. No. 5,772,216 to Bredemeyerand U.S. Pat. No. 5,607,165 to Bredemeyer. Such pressurized dynamicsealing arrangements may be used in the process gas industry for valvesand the like to better ensure that process gas (e.g. natural gas,gaseous fuel, etc.) does not leak or cause a hazardous externalenvironment.

These patents disclose that use of pressurized barrier sealant providesopposing axial fluid forces on two spaced apart seals. In thesearrangements, the barrier sealant fluid pressure is typically greaterthan the process gas pressure such that if leakage is to occur, most orall of the leakage would be the barrier sealant rather than process gas.Indicating mechanisms are disclosed in these patents that indicatewhether sealant leakage is occurring.

The problem with the concepts disclosed in the foregoing patents is thatthe concepts appear to be complex and costly to implement. Morespecifically, these proposals have complex plumbing arrangements, arenot practical to structurally implement, and/or require numerous complexcomponents for establishing a preload barrier. Further, the indicatingmechanism disclosed in at least some of these patents may have accuracyproblems, may not readily indicate the exact source of the problemand/or may be difficult or impractical to implement in the field oracross different applications. Finally as will be appreciated by thepresent invention, these prior art concepts are subject to potentialpremature failure or leakage.

BRIEF SUMMARY

According to one aspect, the dynamic sealing arrangement provides forpreventing leakage of a fluid along a shaft, comprising at least threeseals arranged along the shaft with pressurized barrier sealant betweenthe first and second seals and a collection area to collect any leakedgas or barrier sealant between the second and third seals.

An apparatus including this sealing arrangement includes a housingadapted to receive the fluid. A shaft extends through the housing and ismovable relative thereto. A first seal is supported by the housing andsealingly engages the shaft. A second seal is also supported by thehousing and sealingly engages the shaft in spaced axial relation to thefirst seal. Barrier sealant contained between the first and second sealsis pressurized by a load member to provide opposing axial forces on thefirst and second seals. A third seal supported by the housing sealinglyengages the shaft in spaced relation to the second seal and collectionarea in the housing between the second and the third seals. A collectionpassageway in the housing connects the collection area to an output portwhich can be mounted to instrumentation and/or collection apparatuswhich can be used to determine how well the sealing arrangement isperforming, or it can be plugged and sealed off or vented through afilter that prevents ingress of material.

One aspect of the preferred embodiment is that the third seal isarranged as an external seal proximate the external environment toprevent ingress of dust, grit and other contaminants, thereby ensuringthat the seals which are subject to axial barrier sealant loads are freeof contaminants from the external contaminant that could cause prematurefailure.

In accordance with another aspect, a unitary seal block member isprovided that supports the dynamic sealing arrangement for the shaft anddefines a piston chamber and a drilled passageway connecting the pistonchamber and barrier sealant pressurization chamber between two seals.Thus, a substantial amount of plumbing is self contained in a singlebody minimizing the need for additional components or complexity.

Other aspects, objectives and advantages will become more apparent fromthe following detailed description when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 21 is a cross sectional schematic view (schematic in that the flowpassages are all shown in a single figure to provide a betterunderstanding of the dynamic sealing arrangement in a single figure) ofa seal mounting block for a movable shaft according to an embodiment ofthe dynamic sealing arrangement.

FIG. 2 is an enlarged view of a portion of FIG. 1 to better illustratethe details about the sealing arrangement along the movable shaft.

FIG. 3 is a cross sectional view of a seal mounting block mountedbetween a spring housing and a valve body for sealing against a movableshaft according to an embodiment of the dynamic sealing arrangement.

FIG. 4 is a cross sectional view of the seal mounting block shown inFIG. 3 along a section perpendicular to that taken in FIG. 3 toillustrate the details to the loading piston and the collectionpassageway.

FIG. 5 is a view of a seal assembly similar to FIG. 2 but with fewercomponents in accordance with another embodiment.

DETAILED DESCRIPTION

Referring to FIG. 3, a preferred embodiment of the dynamic sealingarrangement has been illustrated as a seal assembly 10 for preventingleakage of process fluid and for preventing ingress of dirt,contaminants and other foreign material along a movable shaft 12 that ismovable between an open position and a closed position. It is preferablyincorporated into a separate seal block member 14, or other appropriatetype of housing. In the preferred embodiment, the seal block member 14is sandwiched between a spring housing 16 and a valve body 17. Themovable shaft 12 may be linearly and or rotatably translatable. As shownherein, the movable shaft 12 is integrally connected to a valve member20 that slides linearly in the valve body 17 to regulate process fluidflow along a valve passageway 21.

The novel sealing arrangement as shown herein may be employed in anelectrically actuated well head valve as disclosed in Greeb et al., U.S.patent application Ser. No. 10/340,017, filed on Jan. 10, 2003, assignedto Woodward Governor Company, the entire disclosure of which is herebyincorporated by reference. However, it will be understood that certainclaims appended hereto are written in a broad manner and are thereforeintended to cover other applications where sealing occurs between amovable shaft and a housing.

Referring to the seal block member 14, and according to one aspect ofthe invention, it is a single solitary solid steel member that hasformed passageways, ports, bores, chambers and/or holes formed therein.A central stepped bore 22 is formed centrally through the seal blockmember 14 to slidably receive the shaft 12. With the orientation shownin the figures, the stepped bore 22 includes a bottom retaining shoulder24 and a pair of enlarged annuluses 26, 27 that may be used to helpfluid communication into axially spaced chambers 28, 30 (collectionchamber 30, and barrier sealant chamber 28).

The seal assembly 10 is inserted into the bore 22 coaxial about theshaft 12. As shown in FIG. 2, the seal assembly 10 includes three seals32, 34, 36, a pair of perforated spacer rings 38, 40, a plurality ofseal retainer rings 42 a-d, a cylindrical bearing retainer 42 e, awasher 44 and a snap ring 46. The shoulder 24 axially supports andretains the seal assembly 10 at one end while the snap ring 46 that isremovably mounted in an anchor or groove 48 at the other end of the bore22 retains the seal assembly 10 in the bore 22. The seal retainer rings42 a-e (and shoulder 24 at one end which serves as a retainer) areplaced on opposing sides of each of the seals, 32, 34, 36, and allow forsome limited axial movement of the seals 32, 34, 36.

The perforated spacer rings 38, 40 define throughports 50 so as tocommunicate fluid radially through the seal assembly 10. The perforatedspacer rings 38, 40 are arranged in respective annuluses 26, 27 andcommunicate fluid between the shaft surface and the respective annulus26, 27 or inside surface of the bore.

In a preferred embodiment, the seals 32, 34, 36 are of identicalconstruction and are all radial seals (also known as wiper seals), andmay include a generally U-shaped elastomeric member 52 and a generallyU-shaped metal spring member 54 that urges the legs of the elastomericmember 52 inward and outward. In this manner, each of the seals 32, 34,36 sealingly engages radially inward against the shaft 22 and radiallyoutward against the bore 22. The seals 32, 34, 46 are arranged in spacedrelation along the shaft being separated by appropriate spacer rings 38,40 and/or retaining rings 42 a-e.

The first chamber 28 contains any appropriate barrier fluid such asgrease, that is loaded to a pressure typically greater than the pressurein the valve passageway 21. To accomplish loading, the seal mountingblock member 14 defines a barrier fluid passageway 56 that connects thefirst annulus 26 and/or chamber 28 to a formed cylindrical pistonchamber 58 which is also formed in the seal block member 14.

A piston 60 (which may or may not be spring biased) is slidably mountedin the piston chamber 58 with an O-ring gasket 84 between the piston andseal block member. The piston 60 is enclosed in the piston chamber 58 byan end cap 62 that is fastened to the seal block member 14. An levelindicating rod 64 integrally connected to the piston projects axiallythrough a formed bore in the end cap 62. The level indicating rod 64 maybe graduated (e.g. scale marked with spaced markings and/or numbers) toindicate how much barrier sealant fluid is contained in the system. Apair of O-ring seals 66, 68 seal between the end cap 62 and the sealblock member 14 and the level indicating rod 64 and the end cap 62. Aninlet passage 70 defined in the seal block member 14 provides means tofill the piston chamber 58 with barrier sealant fluid. A grease inletport fitting stub 72 is mounted into the entrance port of the inletpassage 70.

One side of the piston 60 acts upon the barrier sealant fluid in thepiston chamber 58 to pressurize the barrier sealant fluid. The otherside of the piston 60 is exposed to the process fluid pressure containedin the valve passageway 21 via a drilled passage 74 extending throughthe seal block member 14. In this manner, the pressure of the processfluid is used to pressurize the barrier sealant fluid which in turn iscommunicated to the chamber between the two internal seals 32, 34. Thepiston 60 is selectively sized such that it may pressurize the barrierfluid to a pressure greater than the fluid pressure in valve passageway21. Specifically a larger face is exposed to the process fluid than thebarrier fluid as a result of the indicating rod 64 which is exposed tothe low pressure external environment (differential piston effect). As aresult, the barrier fluid pressure is self regulating and automaticallyadjusts to changes in process fluid pressure, if any. If desired, othertypes of loading apparatus may be used, such as spring mechanisms,external pressures or loads, and the like that can also exert pressureon the barrier fluid.

If leakage were to occur, which could occur after an extended serviceinterval, leakage would most likely be barrier sealant past either ofthe two internal seals 32, 34 rather than process fluid. Thisadvantageously prevents leakage of process fluid and thereby lowersenvironmental emissions and/or reduces the potential for a hazardouscondition. Further, because barrier sealant would ordinarily be thefluid leaked, the piston 60 would tend to move or push out barriersealant past the seal meaning that the level indicating rod 64 which isrecessed would become exposed and provide an indication that there mightbe a leakage problem.

In one aspect, the barrier sealant system is substantially selfcontained in the single unitary mass of the seal block member 14. Theseal block member 14 may mount directly to a valve body 18 or otherpressurized reservoir or body (e.g. a pump) with a single O-ring staticseal element 76 arranged and compressed therebetween to prevent leakage.No external plumbing, hydraulic couplings, tubes, conduits are needed,which substantially reduces the complexity and provides for reducedpotential for leakage or failure. In addition, the pressurizing piston60 is offset from the shaft 12 which simplifies the construction of theseal assembly 10 and thereby is thought to increase reliability of theseal assembly 10.

In accordance with another aspect, both of the seals 32, 34 which areacted upon by pressurized barrier sealant are internal type seals andtherefore not exposed to mud, dirt, contaminants or other foreign matterfrom the external environment. This is achieved by arranging the thirdseal 36 as the external seal to prevent the ingress of contaminants andpreventing such contaminants from reaching seals 32, 34. As a result,the seals 32, 34 (and particularly seal 34) that are subject to thelargest stresses and pressures are both internal seals that are free offurther stress or wear that would otherwise be induced by foreignmaterial from the external environment.

Even further, there is a significant advantage in that the collectionchamber 30 is formed between seals 34, 36. A drilled collectionpassageway 78 connects an output port 80 on the outside of the sealblock member 14 with the collection chamber 30. This can be used for anumber of purposes depending upon application, including for exampleinstrumentation or a gas or barrier fluid sensor mechanism 82 asschematically shown. The sensor mechanism 82 is adapted to sense leakageof fluid and/or barrier sealant past the second seal. This provides anadditional feature that can sense whether leakage is occurring even ifnot indicated by the level indicating rod for such reasons as if thepiston were to be stuck, or the barrier sealant passageway plugged, orother possible reasons. If gas leakage is occurring rather than barriersealant leakage, then the level indicating rod may not indicate aproblem which the sensor mechanism 82 would. In addition, and dependingupon application, mechanism 82 could alternatively be a plug pluggingthe output port 80,a vent filter mounted to the output port preventingexternal contaminants from acting upon the intermediate seal 34, and/ora pressure relief valve in fluid communication with the collectionpassageway arranged to allow one way flow from the collection area tothe output port. Such a pressure relief valve may have a mechanism on itto show whether it has been opened also identifying whether a problemmay exist.

Another embodiment with fewer components is shown in FIG. 5. In thisembodiment, retainer components 42 a-42 d (see FIG. 2) have beeneliminated. The remaining components are the same and like referencecharacters are used. It will be appreciated that this embodimentfunctions in a similar manner to the first embodiment.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “first”, “second”, and “third” as it pertains tothe seals or other structures are used for purposes of differentiationonly and do not provide any numerical differentiation or relativeposition limitations for the seal or other recited structure. Otherterms are used in the claims for such purposes. The use of the terms “a”and “an” and “the” and similar referents in the context of describingthe dynamic sealing arrangement (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the dynamicsealing arrangement and does not pose a limitation on the scope of theinvention unless otherwise claimed. No language in the specificationshould be construed as indicating any non-claimed element as essentialto the practice of the invention.

Preferred embodiments are described herein, including the best modeknown to the inventors for carrying out the invention. Variations ofthose preferred embodiments may become apparent to those of ordinaryskill in the art upon reading the foregoing description. The inventorsexpect skilled artisans to employ such variations as appropriate, andthe inventors intend for the invention to be practiced otherwise than asspecifically described herein. Accordingly, this invention includes allmodifications and equivalents of the subject matter recited in theclaims appended hereto as permitted by applicable law. Moreover, anycombination of the above-described elements in all possible variationsthereof is encompassed by the invention unless otherwise indicatedherein or otherwise clearly contradicted by context.

1. An apparatus for providing a dynamic sealing arrangement forpreventing leakage of a fluid along a movable shaft, comprising: ahousing receiving the movable shaft therethrough, the shaft movablebetween an open position and a closed position; a first seal in thehousing engaging the shaft; a second seal in the housing engaging theshaft in spaced relation to the first seal; a barrier sealant containedbetween the first and second seals; a load member adapted to pressurizethe barrier sealant contained between the first and second seals; athird seal in the housing engaging the shaft in spaced relation to thesecond seal, the third seal being an external seal exposed to theambient environment and wherein the first and second seals are internalseals protected from the ambient environment by the external seal; acollection area in the housing between the second and the third seals;and a collection passageway in the housing connecting the collectionarea to an output port.
 2. The apparatus of claim 1, further comprisinga sensor mechanism connected to the output port, the sensor mechanismadapted to sense leakage of fluid and/or barrier sealant past the secondseal.
 3. The apparatus of claim 1, further comprising a plug pluggingthe output port.
 4. The apparatus of claim 1, further comprising a ventfilter mounted to the output port preventing external contaminants fromacting upon the second seal.
 5. The apparatus of claim 1, furthercomprising a pressure relief valve in fluid communication with thecollection passageway arranged to allow one way flow from the collectionarea to the output port.
 6. An apparatus having a dynamic sealingarrangement for preventing leakage of a fluid, the apparatus including avalve body defining a fluid passage for communicating the fluid, a valvein the valve body for regulating flow of the fluid, and a shaftintegrally connected to the valve, the apparatus comprising: a sealblock member for mounting to the valve body, the seal block member beinga single unitary body for supporting the dynamic sealing arrangement andfor forming a reservoir, the seal block member defining a shaft boreadapted to slidably receive the shaft; a first seal supported by theseal block member adapted to sealingly engage the shaft; a second sealsupported by the seal block member adapted to sealingly engage the shaftin spaced relation to the first seal; a piston chamber formed into theseal block member at an offset location relative to the shaft bore, thepiston chamber containing a barrier sealant; a piston slidable in thepiston chamber at the offset location, the piston having a piston facearranged to be exposed to the fluid passage; and a barrier sealantpassageway defined by the seal block member connecting the pistonchamber to a barrier sealant area defined between the first and secondseals for communicating barrier sealant.
 7. The apparatus of claim 6further comprising end cap mounted to the seal block member enclosingthe piston chamber.
 8. The apparatus of claim 7 further comprising alevel indicator stem integrally connected to the piston extendingthrough the end cap.
 9. The apparatus of claim 8 wherein the levelindicator stem comprises graduated means for indicating level of thebarrier sealant in the piston chamber.
 10. The apparatus of claim 8further comprising an inlet port defined in the seal block memberconnected to the piston chamber, and a sealant injection fitting mountedinto the inlet port.
 11. The apparatus of claim 8 further comprising afirst cap seal disposed between the end cap and the seal block memberfor preventing leakage therebetween and a second cap seal supported bythe end cap sealingly engaging the level indicator stem for preventingleakage therebetween.
 12. A dynamic sealing assembly for preventingleakage of a fluid along a movable shaft that passes through a formedbore in a housing, the seal assembly comprising: at least three sealsconfigured to be arranged in axially spaced relation along the movableshaft, first spacer means for axially spacing two of said at least threeseals and for communicating pressurized barrier sealant between thefirst and second seals, second spacer means for axially spacing two ofsaid at least three seals and for helping define a collection area forcollecting leakage of the seals.
 13. The dynamic sealing assembly ofclaim 12 further comprising means for securing the seal assembly in aformed bore.
 14. The dynamic sealing assembly of claim 12 furthercomprising a plurality of seal retainer elements arranged betweenadjacent ones of the seals and spacer means for axially engaging theseal retainer elements.
 15. The dynamic sealing assembly of claim 12wherein the at least three seals comprise wiper seals providing aradially outward radial seal and a radially inward radial seal.
 16. Thedynamic sealing assembly of claim 15 wherein each of the at least threeseals comprises a generally U-shaped elastomeric member and a generallyU-shaped spring member applying radially outward force on opposed legsof the generally U-shaped elastomeric member.